Impeller pumps typically include an impeller positioned in a pumping chamber. The impeller contacts the pumping chamber and friction creates heat. Constant water flow is typically required to cool the impeller pumps in order to prevent damage to the impeller and the pumping chamber.
To increase the time period during which impeller pumps can run without water flow, prior art pumps have included impellers constructed from heat-resistant materials. However, the heat-resistant materials can reduce the efficiency of the pump. Other designs have reduced the friction created by the impeller. The higher temperatures the impeller pumps are exposed to can increase mechanical stress on other components, especially seals.